1. Field of the Art
This invention relates to endoscopes which are in wide use in medical fields for intracavitary observations in diagnostic or therapeutic treatments, and more particularly to a joint construction for connecting an angle section of an endoscopic insertion rod between anterior and posterior sections of the insertion rod.
2. Prior Art
Generally, endoscopes largely consist of a rod-like insertion member and a manipulating head assembly which is connected to the proximal end of the rod-like insertion member (hereinafter referred to simply as "insertion rod" for brevity). Depending upon the rigidity of the insertion rod, endoscopes can be classified into a hard type with a hard insertion rod which has a rigid body over its entire length, and a soft or flexible type with a flexible insertion rod which has a soft and flexible body substantially over its entire length except an angle section and a rigid tip end section which are successively connected to the fore end of the flexible body. Flexible endoscopes are introduced into the body of patient by oral insertion, while hard endoscopes are normally introduced by percutaneous insertion through a percutaneously perforated hole as in the case of peritoneoscopes. Even a hard endoscope, which is likewise provided with an illumination window and an endoscopic observation window at the distal end of the insertion rod, needs to be able to secure a broad view field within an intracavitary portion under observation or to be able to give a therapeutic treatment on a particular region of interest. In this regard, it has been known in the art to provide a flexibly bendable angle section between a fore end of a main body of an insertion rod section in the form of a rigid pipe and a rigid tip end section which accommodates endoscopic observation means at the distal end of the insertion rod, thereby to turn the rigid tip end section into a desired direction by remote-controlling the angle section from a manipulating head assembly of an endoscope.
In most cases, the angle section is constituted by a series of flexibly connected angle rings and a resilient outer skin layer of a net or of a flexible synthetic resin material which is fitted around the angle rings. The outermost angle rings at the opposite ends of the angle section are connected to the insertion rod section and the rigid tip end section, respectively. In this regard, as shown in FIG. 5, for example, at the joint of an angle section 1 with an insertion rod section 2, an angle ring 1a at the proximal end of the angle section 1 is securely fixed to a tubular main body 2a of the insertion rod section 2 by soldering or other suitable fixation means through a joint ring 3. An outer skin layer 1b of the angle section 1 is fixed on the joint ring 3 by a line-wrapping layer 4, which is in turn anchored in position by an adhesive 5.
However, in case of an endoscope to be introduced into the body percutaneously as in the case of a peritoneoscope, it has been the general practice to use a so-called trocar as a guide means which provides a path of insertion for the endoscope. As well known in the art, trocars of this sort are constituted by an outer tubular sheath member and an inner sharp-pointed perforator needle which is extractably fitted into the outer sheath member. The outer sheath member is tapered off at its fore end into a sharp blade-like shape in section to eliminate radially stepped portions around the circumference of the perforator needle in assembled state. In order to introduce an insertion rod of an endoscope into an abdominal cavity under the guidance of a trocar of this sort, firstly the perforator needle is set in a fully inserted position within the outer sheath member, with its sharp-pointed end protruded out of the sharp-edged fore end of the outer sheath member. Then, the trocar is introduced into the body of patient, piercing through outer skin layers with the sharp-pointed end of the perforator needle, for example, toward a region of particular interest within an abdominal cavity. Thereafter, the inner perforator needle is extracted from the outer sheath member, and, in place of the perforator needle, an insertion rod of an endoscope is fitted into the outer sheath member of the trocar, protruding a fore end portion of the insertion rod into the intracavitary region of interest. At the time of an endoscopic examination, the intracavitary portion under observation is normally inflated with a pneumoperitoneum gas for the purpose of broadening the view field of the endoscope and at the same time for precluding bruises or other damages to intracavitary wall surfaces. In such a case, it becomes necessary to prevent the pneumoperitoneum gas from leaking to the outside through a clearance between the insertion rod of the endoscope and the outer sheath member of the trocar. This problem has thus far been coped with by tightly fitting the insertion rod in the outer sheath member of the trocar, that is, by minimizing the dimensional difference between the outside diameter of the insertion rod and the inside diameter of the outer sheath member.
However, when an endoscopic insertion rod is tightly fitted in an outer sheath member which is thinned down toward its fore end in the fashion of a sharp knife blade, it is very likely that the adhesive agent, which anchors line-wrapping layers at the joints of the angle section with main body structures of the rigid tip end section and the insertion rod section of the endoscope, be scraped off by the sharp-edged fore end of the outer sheath member, leaving scraped crumbles of the adhesive in the body as the insertion rod of the endoscope is moved back and forth within the outer sheath member. As a countermeasure to this problem, it has also been known in the art to employ a rigid cover ring 6 of a metallic material as a substitute for the above-described adhesive agent, thereby covering the line-wrapping layer 4 at a joint portion as shown in FIG. 6. The rigid cover ring 6 is externally gradually thinned down in and toward its opposite end portions, so that the insertion rod presents a streamlined profile across the cover ring 6, free of radially stepped surfaces.
For receiving an insertion rod with such a rigid cover ring, it is necessary for the trocar sheath member to be able to ride over the rigid cover ring smoothly as the insertion rod is moved back and forth therein. The rigid cover ring is usually fitted on a resilient protective cover tube of a synthetic resin material, which forms an outer skin layer on a body of a joining section or sections of the insertion rod. Therefore, even if the rigid cover ring is thinned down to bring its opposite ends gradually into the level of an underlying resilient skin layer of the insertion rod as smoothly as possible, the end faces of the rigid cover ring tend to stick out radially outward of the underlying resilient skin layer partly due to a discontinuity in rigidity from the rigid cover ring to the resilient outer skin layer and partly due to repeated bending operations of the angle section during use over an extended period of time. If the rigid cover ring sticks out radially outward of the resilient outer skin layer, even in a very slight degree, difficulties are encountered in moving the endoscopic insertion rod back and forth within the outer sheath member, particularly, at the time of extracting the insertion rod out of the trocar, because in that state the sharp-edged fore end of the outer sheath easily comes into abutment against the proximal end face of the rigid cover ring, hindering its retraction into the outer sheath member of the trocar.